javascript isalpha – how to check if a string is alphabetic in javascript?

javascript isalpha – isAlpha. JavaScript, String, Regexp. Use RegExp.prototype.test() to check if the given string matches against the alphabetic regexp pattern.

javascript isalpha – javascript String isalpha() Method

You could just use a case – insensitive regular expression Checks if the character is an alphabetic character.

  • /*/^[a-zA-Z()]*$/ – also returns true for an empty string
  • /^[a-zA-Z()]$/ – only returns true for single characters.
  • /^[a-zA-Z() ]+$/ – also allows spaces*/
  • //better regEX to include question marks too

Example

const isAlpha = str => /^[a-zA-Z]*$/.test(str);
isAlpha('pakaInfo'); // true
isAlpha('welcom To pakainfo'); // false
isAlpha('986565'); // false

Check if a character is alphabetic

`a`.isAlpha(); // true
`i`.isAlpha(); // true
`3`.isAlpha(); // false

Python String isalpha() Method

txt = "pakainfoCom"

x = txt.isalpha()

print(x)

Don’t Miss : JavaScript Tutorial

isalphabetic javascript

function isAlphaOrParen(str) {
  return /^[a-zA-Z()]+$/.test(str);
}

Javascript Function that returns true if a letter?

You can use the String.prototype.match() method along with a regular expression to check if a character is a letter or not in JavaScript. Here’s an example function that returns true if a given character is a letter:

function isLetter(char) {
  return char.match(/[a-zA-Z]/);
}

In this function, the match() method checks whether the char parameter matches any of the lowercase or uppercase letters between a-z or A-Z respectively. If it does, it returns an array of matches, which is a truthy value. If it doesn’t match any letter, it returns null, which is a falsy value.

You can use this function to check whether a given character is a letter or not by calling it with the character as the argument. For example:

console.log(isLetter('A')); // true
console.log(isLetter('a')); // true
console.log(isLetter('1')); // false
console.log(isLetter('%')); // false

In this example, the function returns true for the first two calls since ‘A’ and ‘a’ are letters, and false for the last two calls since ‘1’ and ‘%’ are not letters.

Isalpha, isalnum in Javascript?

In JavaScript, there are no built-in functions named isalpha() or isalnum() as they exist in some other programming languages such as Python or C++. However, you can implement similar functionality using regular expressions and the String.prototype.match() method.

isalpha(): This function is used to check if a string contains only alphabetic characters (A-Z, a-z). You can use the following regular expression to achieve this:

function isAlpha(str) {
  return /^[a-zA-Z]+$/.test(str);
}

In this function, the ^ and $ characters match the start and end of the string, respectively. The [a-zA-Z] part matches any alphabetic character, and the + character means that the previous pattern should match one or more times. The test() method returns a Boolean indicating whether or not the given string matches the regular expression.

isalnum(): This function is used to check if a string contains only alphanumeric characters (A-Z, a-z, 0-9). You can use the following regular expression to achieve this:

function isAlnum(str) {
  return /^[a-zA-Z0-9]+$/.test(str);
}

In this function, the regular expression is similar to the one used in isAlpha(), except that it also includes the digits 0-9 in the pattern.

You can use these functions to check if a string contains only alphabetic or alphanumeric characters, like this:

console.log(isAlpha('HelloWorld')); // true
console.log(isAlpha('Hello123')); // false
console.log(isAlnum('Hello123')); // true
console.log(isAlnum('Hello@123')); // false

In these examples, the functions return true if the given string contains only alphabetic or alphanumeric characters, and false otherwise.

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